<form id="searchform" method="get" action="<?php bloginfo('home'); ?>/">
    <p><input name="s" id="searchfield" type="text" value="Search..." onblur="if(this.value=='') this.value='Search...';" onfocus="if(this.value=='Search...') this.value='';"/><input id="searchsubmit" type="submit" value="" /></p>
</form>